Field of the Invention
The invention relates to a light source module and a light source unit, and more particularly, relates to a light source module and a light source unit having a secondary lens.
Description of Related Art
Generally, a light emitting diode (LED) is applicable on various lighting devices and various flat-panel displays (e.g., as a light source of a liquid crystal display (LCD)) in daily life.
Take the light emitting diode applied in the liquid crystal display for example. A backlight module of the liquid crystal display is a kind of a planer light source, and a basic principle thereof is to convert an effective light from a linear light source or a point light source into the planar light source with high brightness and favorable uniformity. Generally, according to a position of the light source, the backlight module may be classified into two types, namely a edge type and a direct type. Because a direct type backlight module has a simple structure and may adopt a plurality of light sources for providing higher brightness and luminance, the direct type backlight module is often applied in electronic products such as a large size liquid crystal display.
In order to reduce the number of the light emitting diodes or reduce an optical cavity depth, secondary optical lenses are often disposed in some of the direct type backlight modules nowadays. However, a light diffusion capability of the secondary optical lens, the number of the light emitting diodes and the optical cavity depth are factors that affect the product costs. For instance, when the secondary lens used in the direct type backlight module is a refractive secondary lens, which has an opening angle of ±80° and a distance ratio (i.e., h/p ratio) of an optical cavity depth (h, referring to FIG. 1) to a pitch between the light emitting diodes (p, referring to FIG. 1) approximately 0.25, if the optical cavity depth is 25 mm, the pitch between the light emitting diodes requires approximately 100 mm. As the distance ratio of the optical cavity depth to the pitch between the light emitting diodes is lower, the better light diffusion capability of the secondary lens is required. Therefore, when aforesaid secondary lens is used and the direct type backlight module are to be further miniaturized, in order to maintain the same distance ratio of the optical cavity depth to the pitch between the light emitting diodes, the pitch between the light emitting diodes must be reduced. Accordingly, the number of the light emitting diodes and processing costs for attaching the secondary lens to surfaces of supporting the secondary lens may both be increased. As such, how to provide a favorable uniformity and taste for the direct type backlight module while taking the product costs into consideration is an issue to be solved.
China patent application publication no. CN101153982A discloses a backlight module having a bottom plate, a plurality of light emitting diodes disposed on the bottom plate, and an optical plate disposed above the light emitting diodes. Taiwan patent application publication no. 201411892 discloses a lens and a reflective layer. The lens is disposed on a substrate and covers a light emitting diode chip. The reflective layer is disposed on the lens, and configured to reflect a light ray emitted from a lateral side of the light emitting diode chip. Taiwan patent application publication no. 201027184 discloses a backlight module including a reflective plate, at least one light source and at least one lens. U.S. Pat. No. 6,814,456B1 discloses a light shading sheet, which covers a light source generator, and the light shading sheet includes a plurality of light holes for scattering light.
The information disclosed in this “BACKGROUND OF THE INVENTION” section is only for enhancement understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Furthermore, the information disclosed in this “BACKGROUND OF THE INVENTION” section does not mean that one or more problems to be solved by one or more embodiments of the invention was acknowledged by a person of ordinary skill in the art.